1. Chapter 26.5 THE EXPANDING UNIVERSE
Pearson Prentice Hall Physical Science: Concepts in Action Chapter 26 Exploring the Universe
Chapter 26.5 THE EXPANDING UNIVERSE
Welcome again guys. In this presentation we will discuss the Big Bang, the Doppler Effect, Cosmic Background Radiation, and Dark Matter.

2. Hubble’s Law and Red Shifts
Def: The universe is the sum of all matter and energy that exists, that ever has existed, and that ever will exist
In 1929, Edwin Hubble announced that atoms in stars emit light toward the red end of the light spectrum
Hubble’s Law says that the speed at which a galaxy is moving away is proportional to its distance from us
This helped to formulate the evidence to support the Big Bang Theory
Hubble’s Law states that galaxies move away from each other, and that the velocity with which they draw back is relative to their distance. It leads to the picture of an expanding universe and, to the Big Bang theory.

3. Doppler Effect
The Doppler effect is used to determine how fast stars are moving toward or away from Earth
Def: the Doppler effect is the change in wave frequency and wavelength as an object moves toward or away from you
Def: Red shift is a shift toward the red end of the spectrum in the observed spectral lines of stars or galaxies
When a object moves away from Earth, the light source moves away & wavelengths become longer toward the red end of the spectrum
The Doppler effect is used to measure how fast stars are moving toward us or away from us. There are two kinds of effects, Redshift and Blueshift. In Blueshift it shifts to the blue end of the spectrum this means that there is a higher frequency and that the object is moving towards you as the waves bunch up getting closer. This, in sound leads to a higher pitch, and in spectral analysis it is closer to the blue end of the spectrum. Redshift show spectral analysis in the red wavelength end of the spectrum, this means there is a lower frequency of wavelengths so you are seeing less waves as the wavelength is longer. In sound this is a lower pitch because it’s moving away from you. Think of it this way if you were in a wave pool and the waves were hitting the end of the pool at a normal rate there would be an average size of the wave and an average number of waves hitting the other side of the pool. Now if you were to push a large amount of water toward the end of the pool the time between waves would decrease (which is the frequency of waves) and there would be more waves hitting the other side than there was before. So the frequency of waves would decrease and the wavelength between each wave would also decrease, this would be an analogy for blue shift.

4. The Doppler effect clips
Here are some video clips showing the change in sound waves from blueshift to redshift.

5. Expanding universe
The red shift means that every galaxy is moving away from Earth & that the universe is expanding
Every galaxy is also moving away from each other implying that the universe is expanding and was once much smaller
If everything is moving away from each other then the idea is at some point it had to all be bunched up with each other. This helps solidify the expanding universe.

6. The Big Bang
The Big Bang was not an explosion in space, as the theory's name might suggest. Instead, it was the appearance of space everywhere in the universe, researchers have said.
According to the Big Bang theory, the universe was born as a very hot, very dense, single point in space. 
The theory of Big Bang is widely accepted and pretty much says that about 14 billion years ago there was a “hot dense state” when something occurred that triggered the universe to start expanding. Due to the name many people think it was a large explosion, but that’s not the case, it was more like a balloon being inflated and growing in size.

7. Big Bang and Cosmic background radiation (CBR)
It is unclear what happened before this moment but a key part of this comes from observations of the cosmic microwave background, which contains the afterglow of light and radiation left over from the Big Bang.
This remnant of the Big Bang saturates the universe and is visible to microwave detectors, which allows scientists to piece together clues of the early universe. 
So with the idea of the stars in redshift or moving away from us we also add the cosmic microwave background radiation. We don’t know what happened before this but this radiation is like an after glow of light that we can see and is left over from the Big Bang event. This radiation is visible to microwave detectors and allows us to use the scientific process to piece together clues of what the universe was like.

8. Cosmic background radiation continued
When the universe was only a hundredth of a billionth of a trillionth of a trillionth of a second — it underwent an unbelievable expansion (inflation)
It grew exponentially and doubled in size at least 90 times, as it was expanding it became cooler and less dense
As it continued to grow it grew at a slower rate and matter was formed.
At the very beginning the universe underwent this huge and fast expansion. It’s mind boggling and hard to imagine how fast and how large this expansion occurred. But then as it began to occur it started to cool down and become less dense as there was more surface area for it to expand in. It then began to slow down the expansion rate and with the cooler temperatures and the lower density matter was able to form.

9. Big Bang and Cosmic background radiation (CBR)
Light chemical elements were created within the first three minutes of the universe's formation.
As the universe expanded, temperatures cooled and protons and neutrons collided to make an isotope of hydrogen which then combined to make helium. 
Atoms crashed together with enough force to break up into a dense, cloudy plasma of protons, neutrons and electrons that scattered light like fog.
About 380,000 years after the Big Bang, matter cooled enough for electrons to combine with nuclei to form neutral atoms ("recombination") and the absorption of free electrons caused the universe to become transparent.
The light that was released at this time is detectable today in the form of radiation from the cosmic microwave background. 
After about three minutes the universe, while still expanding, cooled enough for the subatomic particles (protons/neutrons/electrons). Everything was crashing into each other which then started to combine to make helium. A dense cloudy fog of these subatomic particles started to scatter the light. Once it cooled enough atoms began to form and the absorption of these electrons caused the universe to become clear. This light is detected still to this day in the form of radiation, we call cosmic background radiation.

10. COSMIC BACGROUND RADIATION
We will assume the universe is about 14 billion years old
In this theory there is no time, no space and nothing at all before the Big Bang
Def: Cosmic background radiation which is a steady, dim radiation detected at microwave wavelengths is believed to support this theory
Expansion is cooling the universe
The red shift also supports the theory
Scientists believe that the universe is still expanding today
Here is just an overview of what we just talked about. Before Big Bang there was nothing, no matter, no time, nothing. As the Universe started to expand and cool light was finally able to be seen and this is called cosmic background radiation which is detected and used to support the theory of Big Bang. When we look at stars they are shifting to the red spectrum, this provides evidence that the Universe is expanding and also helps to support the theory of Big Bang.

11. Dark Matter
Whether or not the universe continues to expand depends on the amount of mass of the entire universe
It is not known for how long the universe will continue to expand
If there is not enough mass, gravity will be too weak to stop the expansion
If mass is just right, expansion will slow down but never stop
When will the universe stop expanding? Well we don’t really know, it will depend on how much mass and gravity. It’s possible that the universe will never stop expanding

12. DARK MATTER PART 2
If there is too much mass, gravity will take over and the universe will contract again, causing a “big crunch” & the whole thing could happen again
The amount of matter is determined by matter that can be seen such as stars, and matter that cannot be seen
Def: Dark matter is matter that cannot be seen directly, but its presence can be detected by observing its gravitational effects on visible matter
Dark matter is matter that does not give off radiation
If there is too much mass still in the universe the gravity will take over and the universe could contract back into the dense state it began with. The matter we are talking about is both matter we can see and matter we cannot see (Dark Matter). Dark matter does not give off any radiation (energy) so it cannot be seen by us, we know it’s there because we can see it’s gravitational effects on things we can see.

13. Expansion ends? The universe contains a lot of dark matter
This amount of matter indicates that there is enough mass to keep the universe expanding
In the past, scientists have discovered that the rate of universe expansion may be increasing
Galaxies are moving apart faster than expected
Scientists have named the mysterious force causing this “dark energy”
If expansion is accelerating, it’s likely that the universe will expand forever
We know there is a lot of dark matter and this indicates that there is a lot of mass to keep the universe expanding. There is some evidence to support the idea that the universe is increasing at a faster rate and that galaxies are moving faster than we had expected. Some believe this is due to the force of dark energy influencing. If this is true than the expansion of the Universe may continue forever.

14. What are the three main concepts that help support the Theory of Big Bang
the red shift of light from galaxies as an indication that the universe is currently expanding,
the cosmic microwave background as the remnant radiation from the Big Bang, and
the observed composition of ordinary matter of the universe, primarily found in stars and interstellar gases (from the spectra of electromagnetic radiation from stars
Summing it all up. What are the three main explainations used as evidence to support the theory of the Big Bang. One is redshift as it shows that the stars are moving away from us, this supports the idea that the universe is still expanding. Cosmic Microwave Background radiation is the left over radiation from the Big Bang, and the composition of matter in the universe is primarily found in stars and stellar gases, which we can see through the sectrum of electromagnetic radiation